Growing Crystals At Home

How to Make Rock Candy

Method #1 (3-7 Days and edible)

Make extra if you plan on eating any!!

Rock Candy Materials

Basically all you need to make rock candy is sugar and hot water. The color of your crystals will depend on the type of sugar you use (raw sugar is more golden and refined granulated sugar) and whether or not you add coloring. Any food-grade colorant will work.

  • 3 cups sugar
  • 1 cup water
  • clean glass jar
  • cotton string
  • pencil or knife
  • food coloring (optional)
  • 1/2 tsp to 1 tsp flavoring oil or extract (optional)
  • Lifesaver candy (optional)
  • pan
  • stove or microwave

Make Rock Candy

  1. Pour the sugar and water into the pan.
  2. Heat the mixture to a boil, stirring constantly. You want the sugar solution to hit boiling, but not get hotter or cook too long. If you overheat the sugar solution you'll make hard candy, which is nice, but not what we're going for here.
  3. Stir the solution until all the sugar has dissolved. The liquid will be clear or straw-colored, without any sparkly sugar. If you can get even more sugar to dissolve, that's good, too.
  4. If desired, you can add food coloring and flavoring to the solution. Mint, cinnamon, or lemon extract are good flavorings to try. Squeezing the juice from a lemon, orange, or lime is a way to give the crystals natural flavor, but the acid and other sugars in the juice may slow your crystal formation.
  5. Set the pot of sugar syrup in the refrigerator to cool. You want the liquid to be about 50°F (slightly cooler than room temperature). Sugar becomes less soluble as it cools, so chilling the mixture will make it so there is less chance of accidentally dissolving sugar you are about to coat on your string.
  6. While the sugar solution is cooling, prepare your string. You are using cotton string because it is rough and non-toxic. Tie the string to a pencil, knife, or other object that can rest across the top of the jar. You want the string to hang into the jar, but not touch the sides or bottom.
  7. You don't want to weight your string with anything toxic, so rather than use a metal object, you can tie a Lifesaver to the bottom of the string.
  8. Whether you are using the Lifesaver or not, you want to 'seed' the string with crystals so that the rock candy will form on the string rather than on the sides and bottom of the jar. There are two easy ways to do this. One is to dampen the string with a little of the syrup you just made and dip the string in sugar. Another option is to soak the string in the syrup and then hang it to dry, which will cause crystals to form naturally (this method produces 'chunkier' rock candy crystals).
  9. Once your solution has cooled, pour it into the clean jar. Suspend the seeded string in the liquid. Set the jar somewhere quiet. You can cover the jar with a paper towel or coffee filter to keep the solution clean.
  10. Check on your crystals, but don't disturb them. You can remove them to dry and eat when you are satisfied with the size of your rock candy. Ideally you want to allow the crystals to grow for 3-7 days.
  11. You can help your crystals grow by removing (and eating) any sugar 'crust' that forms on top of the liquid. If you notice a lot of crystals forming on the sides and bottom of the container and not on your string, remove your string and set it aside. Pour the crystallized solution into a saucepan and boil/cool it (just like when you make the solution). Add it to a clean jar and suspend your growing rock candy crystals.

Borax Snowflake

Method #2

(Overnight to 1 day, not edible)

What You Need

  • string
  • wide mouth jar (pint)
  • white pipe cleaners
  • borax (see tips)
  • pencil
  • boiling water
  • blue food coloring (opt.)
  • scissors

Tips:

Borax is available at grocery stores in the laundry soap section, such as 20 Mule Team Borax Laundry Booster. Do not use Boraxo soap.

Here's How:

  1. The first step of making borax crystal snowflakes is to make the snowflake shape. Cut a pipe cleaner into three equal sections.
  2. Twist the sections together at their centers to form a six-sided snowflake shape. Don't worry if an end isn't even, just trim to get the desired shape. The snowflake should fit inside the jar.
  3. Tie the string to the end of one of the snowflake arms. Tie the other end of the string to the pencil. You want the length to be such that the pencil hangs the snowflake into the jar.
  4. Fill the widemouth pint jar with boiling water.
  5. Add borax one tablespoon at a time to the boiling water, stirring to dissolve after each addition. The amount used is 3 tablespoons borax per cup of water. It is okay if some undissolved borax settles to the bottom of the jar.
  6. If desired, you may tint the mixture with food color.
  7. Hang the pipe cleaner snowflake into the jar so that the pencil rests on top of the jar and the snowflake is completely covered with liquid and hangs freely (not touching the bottom of the jar).
  8. Allow the jar to sit in an undisturbed location overnight.
  9. Look at the pretty crystals!!! You can hang your snowflake as a decoration or in a window to catch the sunlight :-)